1. Field of the Invention
The present invention relates to a recliner adjuster attached to, for example, an automobile seat for appropriately adjusting inclination of a seat back with respect to a seat cushion.
2. Description of the Related Art
In a recliner adjuster disclosed in Japanese Utility Model Publication (examined) No. 42-7950, a sector gear is fixed to a seat back while a worm, which can be freely engaged with and disengaged from the sector gear, is rotatably attached to a seat cushion. The worm is connected to an operation shaft and, by pulling the operation shaft in the axial direction thereof and by subsequently lifting it up, the engagement between the worm and sector gear is released. When a load is applied to the seat back in this state, the seat back tilts and the inclination thereof can be altered quickly. When the hand is released from the operation shaft, the worm and sector gear reengage to hold the seat back in that position. In addition, if fine adjustment of the inclination of the seat back is required, when the operation shaft is rotated to rotate the worm, the sector gear held in engagement with the worm rotates gradually, making it possible to smoothly alter the seat back to a desired inclination.
In another recliner adjuster disclosed in Japanese Laid-Open Patent Publication (unexamined) No. 10-217817, a sector gear and a worm having a lead angle greater than a friction angle are attached to a seat back and a seat cushion, respectively. According to this recliner adjuster, by tilting the seat back, the worm is caused to rotate by way of the sector gear, making it possible to appropriately alter the inclination of the seat back.
However, in the recliner adjuster having a sector gear and a worm held in engagement with each other, a problem sometimes arises in that abnormal noise is generated by backlash which represents play between the teeth surfaces of the sector gear and worm.
To solve this problem, Japanese Laid-Open Patent Publication (unexamined) No. 2000-342371 has proposed reducing the backlash between the sector gear and worm.
In the above-described conventional recliner adjusters, if a large deceleration or acceleration is applied to the vehicle body due to, for example, a collision of the vehicle, a large load is applied to the mating surfaces of the sector gear and worm. In view of this, the strength required to withstand such a large load is ensured by employing a sector gear and a worm of a size greater than a predetermined size. That is, in order to enhance the strength of the recliner adjuster, it is necessary to enlarge not only the sector gear and worm but component parts associated therewith.